BRPI0612885A2 - process for the production of hydrogen peroxide and chlorate - Google Patents

Abstract

The invention relates to a process for the production of alkali metal chlorate comprising: providing an electrochemical cell comprising an anode and a cathode in separate anode and cathode compartments; contacting the cathode with an electrolyte comprising at least one organic mediator and one or more organic or mineral acids; reacting the organic mediator at the cathode to form at least one reduced form of the mediator; reacting the at least one reduced form of the mediator with oxygen to form hydrogen peroxide; contacting the anode with an anolyte comprising alkali metal chloride; reacting chloride at the anode to form chlorine that is hydrolysed; and, reacting the hydrolysed chlorine to form chlorate.

Description

"PROCESS FOR THE PRODUCTION OF ECLORATE HYDROGEN PEROXIDE"

The present invention relates to a process for producing alkali metal chlorate in a divided electrochemical cell.

Alkali metal chlorate, and especially desodium chlorate, is an important chemical, particularly in the pulp and paper industry as a chlorine dioxide-producing raw material that is widely used for bleaching. Alkali metal chlorate is conventionally produced by electrolysis of alkali demetal chloride in open undivided electrolyte cells provided with hydrogen cathodes. Total chemical reaction that occurs in such cells is

MCl + 3H20 MClO3 + 3H2

where M is an alkali metal. The process is very efficient, although the hydrogen gas involved in the cathode creates some overvoltage, increasing energy consumption.

Hydrogen peroxide is also widely used in the pulp and paper industry, and is generally produced by the anthraquinone process involving hydrogenation and oxidation of anthraquinones and / or tetrahydro anthraquinones in an operating solution. Although very efficient, this process is complicated to operate and requires extensive equipment. Alternative processes have so far been proven competitive unless under very special circumstances.WO 2004/005583 discloses production of alkali metal chlorate in an electrolyte cell divided by a selective cation separator in an anode compartment in which an anode is disposed, and a cathode in which gas diffusion electrode is disposed. Oxygen is introduced into the cathode compartment, and electrolyzed to produce alkali metal hydroxide.

The electrochemical production of alkaline hydrogen peroxide solution by reducing oxygen in a cathode is disclosed in, for example, US 6322690.

The electrochemical production of alkaline hydrogen peroxide solution by reducing oxygen in a cathode and simultaneously producing sodium chlorate, is revealed in E.E. Kalu and C. Oloman, "Simultaneous electrosynthesis of alkaline hydrogen peroxide and sodium chlorate" ("Simultaneous electrosynthesis of alkaline hydrogen peroxide and sodium chlorate"), Journal of AppliedElectrochemistry 20 (1990), 932-940.

EL Gyenge and CW Oloman disclose in "Electrosynthesis of hydrogen peroxide in acidic solutions by mediated oxygen reduction in a three-phase (aqueous / organic / gaseous) system Part I: Emulsionstructure, electrode kinetics and batch electrolysis" acid solutions by mediated oxygen reduction in a three-phase system (aqueous / organic / gas) Part I; Emulsion Structure, Electrode Kinetics and Batch Electrolysis "), Journal of Applied Electrochemistry (2003), 33 (8), 655-663e "" Electrosynthesis of hydrogen peroxide in acidicsolutions by mediated oxygen reduction in a three-phase (aqueous / organic / gaseous) system Part II: Experiments inflow-by fixed-bed electrochemical cells with three-phaseflow "(" Electrosynthesis of hydrogen peroxide in acid solutions by a three-phase mediated oxygen reduction (aqueous / organic / gas) Part II: Experiments in a fixed-flow electrochemical cell flow three-phase "), Journal of Applied Electrochemistry (2003), 33 (8), 665-674, hydrogen peroxide production by electroneduction of 2-ethyl-9,10-anthraquinone to the corresponding anthrahydroquinone dissolved in a water-emulsified organic phase. Anthrahydroquinone is reacted with gaseous oxygen to obtain hydrogen peroxide.

JP 61-284591 and US 4067787 disclose hydrogen peroxide production by reducing a water-soluble anthraquinone derivative in an aqueous solution, followed by reaction with oxygen.

A. Huissoud and P. Tissot disclose in "Electrochemicalreduction of 2-ethyl-9,10-anthraquinone on reticulated carbon and mediated formation of hydrogenperoxide" ("Electrochemical reduction of 2-ethyl-9,10-anthraquinone in cross-linked vitreous carbon and mediated formation"). Peroxide "), Journal of AppliedElectrochemistry (1998), 28 (6), 653-657, electrochemical reduction of 2-ethyl-9,10-anthraquinone in dimethoxyethane comprising 5% water and 0.1 mole / liter tetraethylammonium tetrafluorborate .

Electrochemical oxygen reduction in an anthraquinone-grafted decarbon cathode is disclosed, for example, in WO 02/02846, Mirkhalaf, Fakhradin; Tammeveski, Kaido; Schiffrin, David J., "Substituting effects on the electrocatalytic reduction of oxygen on quinone-modifiedglassy carbon electrodes" ("Substituted effects on the electrocatalytic reduction of oxygen on quinone vitreomodified carbon electrodes"), Phys. Chem. Chem. Phys. (2004), 6 (6), 1321-1327, and Vaik, Katri; Schiffrin, David J. Tammeveski, Kaido; "Electrochemical reduction of oxygen on pre-treated and chemically grafted glassy carbon electrodes in alkaline solutions" ("Electrochemical reduction of oxygen in anodically pretreated and chemically grafted in alkaline solutions"), Electrochemistry Communications (2004), 6 (1), 1-5.

Vaiki, Katri; Sarapuu Ave; Tammeveski, Kaido; Mirkhalaf, Fakhradin; Schiffrin, David J. "Oxygen reductionon phenanthrenequinone-modified glassy carbon electrodes in 0.1M KOH" ("Oxygen reduction in phenanthrenequinone modified carbonovitre electrodes in 0.1M KOH"), Journal of Electroanalytical Chemistry (2004), 564 ( 1-2), 159-166, disclose the use of a phenanthrenequinone grafted cathode.

WO 03/004727 discloses electrosynthesis of organic compounds by electrochemical transformation of a compound in the presence of an electrolyte comprising ionic liquid at room temperature and product recovery.

It is an object of the invention to provide an efficient process for the production of alkali metal chlorate.

It is another object of the invention to provide a process which enables simultaneous production of metal alkaline chlorate and hydrogen peroxide.

The invention relates to a process for the production of alkali metal chlorate comprising:

providing an electrochemical cell comprising a node and a cathode in anode and cathode-separated compartments;

cathode contact with a catholyte comprising at least one organic mediator and one or more organic or mineral acids;

reaction of the organic mediator in the cathode to form at least a reduced form of the mediator;

reacting at least one reduced form of the oxygen mediator to form hydrogen peroxide;

contacting the anode with an anolyte comprising alkali metal chloride;

reaction of chloride on the anode to form chlorine which is hydrolyzed; and

hydrolyzed chlorine reaction to form chlorate.

Preferably the hydrogen peroxide is separated from the catholyte as a product, or used as a reagent for the production of other chemicals without separation from the electrolyte. However, where hydrogen peroxide is not required at the place of production, it is also possible to simplify the destruction of hydrogen peroxide, for example by catalytic decomposition.

The anolyte may have a chloride ions saturation concentration, preferably from about 30 to about 300 g / l, more preferably from about 50 to about 250 g / l, more preferably from about 80 to about 200 g / l. , calculated as sodium chloride. The anolyte usually also comprises at least some chlorate, preferably from about 1 to about 1200 g / l, calculated as sodium chlorate. In one embodiment, the preferred content is from about 300 to about 650 g / l, more preferably from about 500 to about 650 g / l, calculated as sodium chlorate. In another embodiment, the preferred content is from about 1 to about 50 g / l, more preferably from about 1 to about 30 g / l, calculated as sodium chlorate.

In order to stimulate chlorine hydrolysis, the pH of the anolyte mass is preferably at least about 4, more preferably from about 4 to about 10. It is understood that there may be local variations in pH, and particularly that there may be there are local zones having considerably lower pH as protons are formed.

In order to suppress unwanted side reactions, it may be possible to include alkali metal chromate, dichromate, or other suitable pH buffer in the anolyte. If chromate or dichromate is present in the anolyte, its content is preferably from about 0.01 to about 10 g / l, more preferably from about 0.01 to about 6 g / l, calculated as sodium chromate. However, it is also possible to operate in the substantial absence of chromate in the anolyte.

Unless otherwise noted, all concentrations in g / l refer to the volume of the current solution.

The temperature in the anolyte is preferably from about 20 to about 100 ° C, more preferably from about 40 to about 90 ° C.

Suitably, much of the chlorine generated in the anode compartment is dissolved in the anolyte solution. Spontaneously dissolved chlorine supports partial hydrolysis to form hypochlorous acid according to the formula:

Cl2 + H2O HClO + HCl

Hypochlorous acid supports disproportionation (in some literature referred to as auto-oxidation) in chlorate according to the total formula:

2HC10 + C10 "-» ClO3 "+ 2 Cl" + 2 H +

Disproportionation may occur in the cell, in a separate chlorate reactor, or a combination thereof.

Preferably, the anolyte from the anode compartment, also referred to as chlorate electrolyte, usually comprising chlorine and / or hypochlorous acid, is brought into a chlorate reactor to proceed with disproportionate reactions to produce chlorate. The chlorate reactor may be of any conventional type, for example as described in US 54 19818, and may comprise one or more chlorate vessels.

When the disproportionation is completed to a sufficient degree, the chlorate electrolyte may be brought into a crystallizer to precipitate and remove solid alkali metal chlorate. The mother liquor from crystallization, usually containing unreacted chloride ions, hypochlorite, and chlorate, is then preferably recycled to the anode compartment of the electrochemical cell to form an anolyte along with alkali metal chloride added. It is also possible to use the chlorate electrolyte as such without crystallization, for example as a feed to a chlorine dioxide generator. This embodiment is advantageous in an integrated process where generator liquor depleted from chlorine dioxide production is recycled back to the electrode cell anode compartment for chloride production.

The production of alkali metal chlorate can be performed continuously, in batch, or in a combination of these.

The organic mediator in the catholyte is preferably dissolved in a predominantly aqueous liquid phase or a predominantly organic liquid phase, preferably having an electrical conductivity under process conditions of at least about 0.1 S / m, more preferably at least about 1 S / m 2. m, more preferably at least about 3 S / m. However, it is also possible for the organic mediator to be dissolved in a predominantly organic phase emulsified to a predominantly aqueous phase. The organic mediator is a substance capable of being electrochemically reacted in a cathode to produce one or several reduced forms, which in turn are capable of reacting. with preferably molecular oxygen, and be converted back to the original form thereby enabling a cyclic process. Reaction of the reduced tamer forms with oxygen preferably occurs in the presence of deprotons. However, in the absence of a suitable proton source, it is possible to form peroxide salts, for example Na2O2, which can subsequently be hydrolyzed to produce hydrogen peroxide. Without being bound by any theory, it is believed that the hydrogen peroxide producing reaction scheme comprises the transfer of two electrons and two protons occurring in simultaneous separate or combined reactions, and is believed to be involved as intermediate species: O2 ', H00 "and HOCT.

Examples of classes of organic substances that form redox systems, and useful as mediators, include quinones, flavoquinones, pyridine derivatives, such as comonicotineamides, and ketones.

Useful quinones include molecules containing a portion of (benzo) quinone (ortho- or para- forms) of which anthraquinones, tetrahydro anthraquinones, naphthoquinones, benzoquinones and derivatives thereof are preferred.

Anthraquinones, naphthoquinones and benzoquinones are preferably substituted, for example substituted alkyl similar to 2-alkyl-9,10-anthraquinones. Specific examples include 2-ethyl-9,10-anthraquinone, 2-tert-butyl-9,10-anthraquinone, 2-hexenyl-9,10-anthraquinone, alkyl-9,10-anthraquinone mixtures and mixtures of 2-amyl 9,10-anthraquinones, all of which have high stability. Specific examples of alkyl substituted naphthoquinones include 2-methyl-1,4-naphthoquinone, 2-ethyl-1,4-naphthoquinone, 2-propyl-1,4-naphthoquinone, 2-tert-butyl-1,4-naphthoquinone, 2- tert-amyl-1,4-naphthoquinone, 2-iso-amyl-1,4-naphthoquinone, 2,3-dimethyl-1,4-naphthoquinone. Other examples of substituents useful for controlling quinone solubility and reactivity include -SO 3 H / -SO 3 -, -OPO 3 R ", -NO 2, -OCH 3, -SO 2 CH 3, -OPh, -SPh, -SO 2 Ph, -C00H / -C00", -CN , -OH, -COCH3, -F, -Cl, -Br, -CF3, -NH2 / NH3 +, -NRH / -NRH2 +, -NR2 / -NR2H +, -NR3 +, -PH2 / -NH3 +, -SR2 +, -PRH -PRH2 +, -PR2 / -PR2H + and -PR3 +, R preferably independently being one of the others, optionally alkyl, alkenyl or substituted aryl, or hydrogen. Anthraquinones may be simply or multiple substituted with a combination of the above substituents, and / or other substituents. It is also possible to use quinone derivatives having common charge-bearing substituents imposing a molecule ionic character. Specific examples of substituted semalkyl quinone derivatives include anthraquinone-2-sulfonate, 5,6,7,8-tetrahydro-9-10-anthraquinone-2-sulfonate, anthraquinone-2,6-disulfate, naphthoquinone-2-sulfonate, 2 -methoxy-1,4-naphthoquinone, 2-ethoxy-1,4-naphthoquinone, 2-amino-anthraquinone, 2-amino-naphthoquinone, 2- (alkylamino) anthraquinone, 2- (dialkylamino) anthraquinone, 2 - (trialkylammonium) anthraquinone, 2- (alkylamino) naphthoquinone, 2- (dialkylamino) naphthoquinone, 2- (trialkylammonium) naphthoquinone. Naphthoquinones may, for example, be substituted at any position on the side ring, for example naphthoquinone-6-sulfonate or 6-trialkylammonianaphtoquinone. A substituent on each ring may also be advantageous, such as 6-amyl-naphthoquinone-2-sulfonate or 6-ethyl-2-triethylammonium naphthoquinone. Corresponding examples for benzoquinone are benzoquinone-2-sulfonate and 2- (ethyl, dimethyl) ammonium. Anthraquinones and naphthoquinones with partially hydrogenated side rings, for example 1,2,3,4-tetrahydro anthraquinone, 5,6,7,8-tetrahydro-2-ethyl anthraquinone, 5,6,7,8-tetrahydroftoquinone, may also be used. This also applies to anthraphosphenated quinones, including those corresponding to the above mentioned types.

In this case, a quinone is substituted and comprises one or more substituted alkyl, alkenyl or aryl groups, it is preferred that these groups independently of one another have from 1 to 12 carbon atoms, more preferably from 1 to 8 carbon atoms. If more than one such group is present, they are preferably of mixed chain length. Alkyl, alkenyl and aryl groups may also be substituted with, for example, one or more hydroxyl groups.

Quinones, including anthraquinones, tetrahydroanthraquinones, naphthoquinones, benzoquinones and derivatives thereof, may be reduced to corresponding hydroquinones by the successive addition of two electrons and two protons. Following quinone and hydroquinone, a number of intermediate forms are believed to be present and active, similar to the semi-quinone radical and the dysquinone anion, as well as the base forms of hydroquinone acid. All of these reduced forms can react as oxygen, and contribute to the overall reaction that produces hydrogen peroxide and the original quinone.

Other mediating systems capable of reducing oxygen to superoxide and subsequently hydrogen peroxide include flavoquinone, eg flavin (see, for example, H. Tatsumi and others in "Mechanistic study of reduced flavin and quinone compounds"). of auto-oxidation of reduced flavin and quinone compounds ") in Journal of Electroanalitycal Chemistry (1988), 443, 236-242), and nicotinamide-like pyridine derivatives and derivatives thereof.

Additional mediating systems are formed by ketones and their corresponding alcohols. Ketone may be electrochemically reduced to the corresponding alcohol, oxygenated to form hydrogen peroxide and original acetone. Secondary alcohols are particularly preferred phenyl alcohols. Useful alcohols include isopropyl alcohol, benzyl alcohol, diphenylmethanol, methylphenylmethanol. Secondary alcohols also containing a group bearing a charge may also be used.

The organic mediator content, including reduced forms, in the catholyte is preferably at least about 0.1 wt%, more preferably at least about 1 wt%, more preferably at least about 3 wt%.

It is limited upwards only by the solubility, which depends on the mediator used and the liquid phase composition, but in many cases being greater than about 10 weight% or about 30 weight%, or even higher. In a embodiment where a significant part of hydrogen peroxide is formed outside the cell, the organic mediator content is preferably at least about 1 weight%, more preferably at least about 3 weight%, more preferably at least about 10 weight%.

If the catholyte comprises a predominantly aqueous continuous phase that dissolves the organic mediator, this phase preferably comprises at least about 50 wt%, more preferably at least about 80 wt% water and other inorganic components. It is then preferred that the mediator be selected from those with high water solubility, for example, quinones comprising one or more hydrophilic groups, such as -SO3H / -SO3 ", -NO2, -C00H / -C00", -OH -NH2 / NH3 +, -NR2 / -NR2H +, -NR3 +, -PH2 / -NH3 +, -PRH / -PRH2 +, -PR2 / -PR2H + and -PR3 +, preferably independently of each other hydrogen, or optionally alkenyl or substituted aryl.

If the catholyte comprises a predominantly organic continuous phase that dissolves the organic mediator, this phase preferably comprises at least about 50 weight%, more preferably at least about 80 weight% inorganic components, and may, in extreme cases, be substantially free of inorganic compounds. However, it is preferred that at least about 5 wt%, more preferably at least about 20 wt% inorganic components are included. Such inorganic components may, for example, be desal inorganic ions produced from both organic and inorganic ions.

The continuous liquid phase of the catholyte preferably comprises an at least partially organic salt comprising at least one type of organic cation and / or organic anion. The content thereof in the continuous liquid phase is preferably from about 20 weight% to about 99 weight%, more preferably from about 40 weight% to about 95 weight%, more preferably from about 60 weight% to about 90 pesol.

The continuous liquid phase of the catholyte has a pH below 7. If the liquid phase is predominantly organic, the pH refers to the pH obtained in water maintained in equilibrium with the predominantly organic liquid phase.

The at least partially organic salt may be selected from the group of salts referred to as ionic liquids, a diverse class of liquids substantially consisting of ions. An ionic liquid may be simple, and contain a simple type of anions and a simple type of cations, or may be complex, and contain a mixture of different anions and / or different cations.

Some ionic liquids have a low melting point, negligible vapor pressure near or below ambient temperature, and are often referred to as ambient temperature ionic liquids. Such liquids usually remain liquids over a large temperature range.

The at least partially organic salt may also be selected from salts which are not only classified as ionic liquids, but have such properties when present together with a cosolvent neutral, such as water or a low molecular alcohol similar to methanol, ethanol or propanol, of which Water is preferred.

The weight ratio of salt to co-solvent is preferably from about 1: 1 to about 1000: 1, more preferably from about 2: 1 to about 100: 1, more preferably from about 5: 1 to about 100: 1. 20: 1.

It is preferred to use an at least partially organic salt which itself, or in combination with a co-solventeneutral, forms a liquid phase at atmospheric pressure below about 130 ° C, preferably below 100 ° C, more preferably below about 80 ° C. . Additionally, the partial pressure of the salt at 100 ° C is preferably below about 10 kPa, more preferably below about 1kPa, more preferably below 0.1 kPa (excluding partial pressure from a neutral optional co-solvent).

A liquid with suitable physical properties may comprise one or a mixture of two or more partially organic salts of salt in combination with neutral cosolvents, of which water is preferred. It may also comprise anions and cations which alone do not form adequate properties. At least partially organic salt may be formed from various combinations of cations and anions, among which one type of ion is organic. The ions are preferably monovalent. Examples of cations include 1-alkyl-3-methyl imidazolium, 1-butyl-3-methyl imidazolium [BMIM], 1-ethyl-3-methyl imidazolium [EMIM], 1,2,3-trimethylimidazolium, N-alkylpyridinium, N- butyl pyridinium [BPY], pyrrolidinium, guanidinium and alkyl guanidinium, isouronium, PR4 +, NR4 +, SR3 "1", tetramethylammonium, choline, cocomonium, and mixtures thereof, R being independently independently of each other, optionally alkyl, alkenyl or substituted aryl , or hydrogen. Other examples include substituted quinones denoted herein [Q-NR3 +] and [Q-PR3 +], where Q represents a quinone such as anthraquinone, naphthoquinone or benzoquinone, and R as described above. Examples of anions include hexafluorophosphate [HFP], tetrafluorborate [TBF], fluororsulfonate, hexafluorantimonate hexafluorarsenate, chloraluminate, bromoaluminate, bis (trifluoromethylsulfonyl) imide, tris (trifluoromethylsulfonyl) methoxy, tricyomethanesulfonate, 2,2-trichloromethane, trifluoroethanesulfonate, nitrate, sulfate, RPO42 ", R2PO4-, R2PO2" (for example a dialkylphosphinate), perchlorate, acetate, alkylsulfonate, bis (2-ethylhexyl) sodiumsulfosuccinate, diethylene glycolmonomethyletersulfate, alkyloligoetersulfate, pylate succinate, pivalate succinate, pivalate succinate glycolate, stearate, lactate, malate, tartrate, citrate, ascorbate, glutamate, benzoate, salicylate, methanesulfonate, toluenesulfonate, mixtures thereof, R as above. Other examples include substituted quinones denoted herein [Q- (O) -SO3] and [Q- (O) -PO3R], where Q represents a quinone such as anthraquinone, naphthoquinone or benzoquinone, (0) denotes an optional oxygen (e.g. sulfate / sulfonate ephosphate / phosphate), and R being as above.

In this case, any cation or anion comprises one or more optionally substituted alkyl, alkenyl or aryl groups, it being preferred that these groups independently of each other have from 1 to 12 carbon atoms, more preferably from 1 to 8 carbon atoms.

If more than one such group is present, they are preferably of mixed chain length. Alkyl, alkenyl and aryl groups may also be substituted, for example, with one or more hydroxyl groups.

Examples of salts useful for the present invention include any combination of the following cations: [1,3-dialkyl imidazolium], [trialkylammonium], [trialkylammonium], [trialkylphosphonium], [tetraalkylphosphonium], [alkylpyridinium], [choline], [Q- NR3 +] and [Q — PR3 +], in combination with any of the following anions; [sulfate], [phosphate], [alkyl sulfate], [alkyl sulfonate], [dialkyl phosphate], [alkyl phosphonate], [Q- (O) -SO3] and [Q- (O) -PO3R], where Q, (0) and R are as defined above.

Specific combinations of groups include [1,3-dialkyl imidazolium] [alkyl sulfonate], such as any of [1-butyl-3-methyl imidazolium] [methyl-SO 3 ~], [1-ethyl-3-methyl imidazolium] [ ethyl sulfonate], [1-hexyl-3-methyl imidazolium] [thisolate], [1-butyl-3-methylimidazolium] [anthraquinone-2-sulfonate] or [1-butyl-3-methylimidazolium] [5-tert-amyl [naphthoquinone-2-sulfonate]; [tetraalkylammonium] [Q- (O) -SO 3], such as any of [methyl, triethyl ammonium], [5-tert-amyl-naphthoquinone-2-sulfonate], [methyl, di-ethyl, butyl ammonium] [anthraquinone-2-sulfonate] or [choline] [5-amyl-benzoquinone-2-sulfonate]; or [Q-NR 3+] [alkyl sulfonate] such as [5,6,7,8-tetrahydroanthraquinone-2-aminium, N, N, N- (methyl, diethyl)] [methylsulfonate]; [tetraalkylphosphonium] dialkylphosphate], such as any of [ethyl tributylphosphonium] [diethyl phosphate], [phenyl triethylphosphonium] [diisobutyl phosphate].

Not being bound to group-specific combinations, a multiplicity of combinations are possible, such as one of [triisobutyl (methyl) phosphonium] [thisolate], [trihexyl (tetradecyl) phosphonium] [bis 2,4,4,4-trimethylphenylphosphinate] [tetrabutylammonium] ] [methanesulfonate] [1-ethyl-3-methyl imidazolium] [HFP], [tripentyl sulfonium] [dipentyl, benzyl ammonium], [benzoquinone-2-aminium-N, NN-diethyl, phenyl] [5,6,7 , 8-Tetrahydro-9,10-anthraquinone-2-sulfonate], [choline] [5-ethoxy-1,4-naphthoquinone-6-sulfate], [N-propyl-pyridinium] [saccharate].

In addition to those mentioned above, other types of ionic liquids or commercially available or otherwise known salts having such properties in combination with a co-solvent may be used.

It may be possible to use a salt where at least one of the ions also acts as a mediator that is reacted nocatode to a reduced form and thereby precipitates the cyclic process for hydrogen peroxide generation. In this case, the mediator used may partially be completely may consist of ions from such a salt. Examples include salts comprising a cation or anion of a substituted quinone or a nicotinamide derivative such as that mentioned above.

The use of at least partially organic salt, as described above, in the continuous phase of the electrolyte involves the advantages of combining high solubility of quinone-like organic mediators with electrical good conductivity. Another advantage is the very low flammability that allows the reaction with oxygen to be safely carried out at higher oxygen concentrations, and higher temperature than would be the case with conventional flammable solvents. It is also easy to separate hydrogen peroxide from it, for example by evaporation and extraction, and thereby obtaining high purity or hydrogen peroxide, or in a mixture with a compound selected for further processing, for example water. Another example is a methanol / hydrogen peroxide mixture for use as a reagent in a oxidation reaction. The use of ionic liquids to form a suitable means for effecting reactions involving hydrogen peroxide has been disclosed in B. Chhikara et al. in "Oxidation of alcohols with hydrogen peroxide catalyzed by a new ion imidazolium-based phosphotungstate complex in ionic liquid", Journal of Catalysis 230 (2005, 436-439).

The catholyte further comprises one or more mineral acids or minerals similar to formic acid, acetic acid, monochloric acetic acid, benzoic acid, sulfonic acids, phosphoric acids, nitric acid, sulfuric acid, hydrochloric acid, hydrobromic acid, perchloric acid, or phosphoric acid.

The catholyte may also comprise other components. For example, a predominantly organic continuous liquid phase may comprise a neutral co-solvent as mentioned above, preferably water. The amount of neutral co-solvent is preferably up to about 50 weight%, more preferably about 1 to about 20 weight%. A particularly preferred co-solvent content may, for example, be from about 1 weight% to about 5 weight%, or from about 5 to about 10 weight%. Examples of other optional additives include hydrogen peroxide stabilizers, emulsifiers, corrosion inhibitors, defoamers, buffers, conductivity enhancers, viscosity reducers, etc. Examples of hydrogen peroxide stabilizers include those commonly used, such as phosphoric acid, phosphoric acid-based complexing agents, alkali demetal stannate-like protective colloids, and similar pyridine carboxylic acid radical purifiers. Examples of phosphoric acid-based decomplexing agents include 1-hydroxyethylidene-1,1-diphosphoric acid, 1-aminoethane-1,1-diphosphoric acid, aminotri (methylenephosphonic acid), ethylene diamine tetra (methylenephosphonic acid), hexamethylene diamine tetra (acid methylenophosphonic acid), diethylenetriamine penta (methylenephosphonic acid), diethylenetriamine hexa (methylenephosphonic acid), 1-aminoalcanate-1,1-diphosphonic acids (such as commorpholinomethane diphosphoric acid, N, N-dimethyl aminodimethyl acid diphosphonic acid, diphosphonic acid products) of these, preferably sodium salts.

It is preferred that the at least partially organic liquid phase has a viscosity under operating conditions below about 100 mPas, more preferably below about 30 mPas, and more preferably below about 10 mPas. Additionally, due to the inherent risks of handling substantially pure hydrogen peroxide, the recovered product is preferably a mixture of hydrogen peroxide with water or low molecular alcohols, for example methanol. The partial pressure at 100 ° C of the liquid components not forming part of the product mixture should preferably be below 10 kPa, more preferably below about 1 kPa, more preferably below 0.1 kPa.

The electrochemical cell may comprise only one anode compartment and one cathode compartment, or additionally comprise one or more compartments therebetween, for example, an electrodialysis stack that causes any known electrodialysis to be performed. The means for separating the compartments may be a non-selective physical barrier, for example a porous membrane or diaphragm, or may be selectively permeable to certain species, such as cations or anions. Also a combination of membranes can be used, such as bipolar membranes that enable the division of water into protons and hydroxide ions. Non-selective barriers can, for example, be produced from asbestos, ceramics, glass, polyolefins, PTFE, PVC, etc. Cation-selective membranes may, for example, be produced from organic polymers such as PTFE, polystyrene, styrene / divinylbenzene, modified vinylpyridine / divinylbenzene with sulfonate, carboxylate or phosphonate-like acid groups. Anion-selective membranes may, for example, be produced from organic polymers, such as PTFE, polystyrene, styrene / divinylbenzene, audiinpyridine / divinylbenzene modified with quaternary ammonium basic groups. A bipolar membrane may comprise an anion permeable membrane and a cation permeable membrane laminated together, optionally with a catalyst layer therebetween. Deion and bipolar selective membranes are commercially available, for example, under the trademarks Naflon®, Flemium ™, Neosepta bipolar®. The cathode compartment electrolyte may contain one, two or more liquid phases. In a simple phaseliquid system, there is only one predominantly organic electrolyte-liquid phase, or one predominantly aqueous liquid electrolyte phase. In a system with two liquid phases, non-continuous phases may be pulsed or simply mixed into the continuous liquid phase. If there is more than one simple liquid phase, the components in the electrolyte will be distributed between phases depending on their solubility properties. Liquid phase or gas, or solid solids may be present.

In the cathode compartment, the temperature and pressure may be the same or different from the anode compartment, and are preferably adjusted so that the catholyte is liquid. A high temperature favors low viscosity, high electrical conductivity and high mass transfer rates, while a low temperature favors the stability of hydrogen peroxide and electrolyte components. Usually the temperature is preferably from about 0 to about 200 ° C, more preferably from about 40 to about 150 ° C, more preferably from about 60 to about 100 ° C. The pressure is preferably from about 10 to about 30000 kPa, more preferably from about 80 to about 2000 kPa, more preferably from about 100 to about 800 kPa. The reaction of one or more reduced forms of the oxygen mediator to Producing hydrogen peroxide may occur within the cell, or in a separate vessel, or a combination of the two, resulting in the formation of hydrogen peroxide in the catholyte and reformation of the mediator to part in another reaction cycle. Normally molecular oxygen is added to the electrolyte comprising reduced media, but part of it may come from the oxygen generated in the anodic reactions, and transported through the cell electrolyte, optionally via a membrane, or be isolated as a separate current, and re-introduced into the cell. Molecular oxygen may be added dissolved in a liquid, or in the form of any oxygen-containing gas, such as air, oxygen enriched, or substantially pure oxygen.

Adding at least part of oxygen as a gas directly into the cell has the advantage of optimizing agitation, and can also create a gas lift for electrolyte transport outside the cell, alternatively contributing to the removal of hydrogen peroxide from the electrolyte. The addition of oxygen directly to the cell can cause the total catalytic cycling cycle to be completed within the cell, substantially eliminating the need for withdrawal of a chain comprising a reduced form of the mediator, and feeding a current comprising a mediator. Reactions to produce hydrogen peroxide are facilitated by the presence of protons that can originate from any available source, such as water, hydroquinone, anode-generated protons, and any acid that has been added to the electrolyte. If the reaction with oxygen occurs in a separate vessel, conditions similar to temperature, pressure, etc. may be the same or different from those prevailing in the cell. The temperature is preferably ambient, for example, about 20 °, at a super-determined limit, either by solvent flammability or by hydrogen peroxide stability, for example, up to about 70 ° C. The pressure is preferably from about thermospherical to about 5 barg. It is generally preferred to use a bubble column, either packed or with plaques. Preferably oxygen-containing gas is fed deep, and the liquid flows either upwardly or downwardly.

Several methods can be used to separate hydrogen peroxide from the electrolyte, such as evaporation, extraction, or membrane-based technologies. Separation can occur in the cell, in separate equipment where the remaining electrolyte is recycled back to the cell, or a combination. of these.

In one embodiment, hydrogen peroxide is evaporated from a predominantly organic phase, preferably together with water and optionally other volatile substances that may be present. Evaporation may be effected directly from the cell, or from a separate vessel, for example, removed with any gas, for example oxygen, air or nitrogen, or by distillation at atmospheric or sub-atmospheric pressure. A low vapor pressure of at least partially organic salt and other organic species optionally present in the electrolyte and not forming the desired product mixture facilitates the use of evaporation techniques for hydrogen peroxide separation.

In this embodiment, a hydrogen peroxide containing the high purity product stream can be obtained in extensive purification steps.

In another embodiment, hydrogen peroxide is extracted from the predominantly organic liquid phase by any suitable solvent, such as water or methanol. All commonly used extraction technologies can be used, such as one or more mixer-settlers, sieve plate columns, packed bed columns. If an electrolyte also comprising a predominantly aqueous phase is used, hydrogen peroxide will be automatically enriched at this stage, which may be withdrawn as a product, alternatively subjected to distillation, or other purification, and recycled back to the cell.

In a further embodiment, membrane based separation is used. Examples of such processes include membrane extraction, pervaporization and nanofiltration.

In yet another embodiment, the mediator and its reduced forms are dissolved in a predominantly aqueous phase. If oxidation of the reducing domesters also occurs in the predominantly aqueous phase, hydrogen operoxide may be separated by, for example, distillation. Another option is to keep the predominantly aqueous phase free of oxygen, and separate, for example by extraction, the reduced forms of the mediator into a predominantly organic phase, then effect oxidation.

In yet another embodiment, hydrogen peroxide is not withdrawn from the electrolyte, but is directly used as a reagent in the production of other chemicals. The electrolyte that remains after such reactions can then be recycled to the cell.

Hydrogen peroxide production is preferably operated continuously, either with electrolyte flowing through the cell, or by continuously separating hydrogen peroxide from the electrolyte in the cell. It is preferred to serve for proper agitation, particularly around the method, for example by gas blowing, mechanical agitation, electrolyte circulation, or combinations thereof. The blast is preferably made with oxygen or oxygen-containing gas, such as air. In a cell with a substantially vertical flow, the gas blow may also create a gas lift that increases electrolyte transport through the cell by alternatively removing hydrogen peroxide, optionally along with water, or any other component that is volatile in operating temperature and pressure.

In order to avoid detrimental accumulation of feed chemical impurities or degradation of side-formed products, it may in some cases be advisable to drain part of the electrolyte from the system, and / or to purify with various methods similar to electrodialysis, adsorption. , recrystallization, precipitation, washing, ion exchange, evaporation, orifice, using a carrier gas, reactive acid / base regeneration or reductive / oxidative steps.

As hydrogen gas may be formed as a side reaction in the cathode, it may be appropriate to include a gas analyzer and a gas-flooding device.

The temperature may be controlled by any suitable means, for example by heat exchangers in any appropriate flow. Cooling can also be effected by evaporation, for example in the electrochemical cell, and subsequent steam condensation. If evaporative cooling is performed by water, it may be appropriate to add water specifically for this purpose.

The anode may be made of any suitable material, for example titanium and titanium alloy. The anode is preferably coated with, for example, RUO2 / T1O2, RuC2 / Ti02102. Particularly preferred, the anodes are DAS ™ (stable size anode).

Various types of cathode may be used. It is preferred that the cathode is produced from a material that has parasitic supimerizations similar to hydrogen evolution, direct reduction of oxygen to water, and destruction of the organic mediator, ionic liquid or hydrogen peroxide formed. In many cases it is preferred to use a cathode with a hydrophobic surface. Examples of ocatode materials include boron-doped similarly carbon-based materials, graphite, vitreous carbon, highly oriented graphite pyrolytic, cross-linked carbon and conductive polymers. Examples of conductive polymers include poly (para) phenylene, polypyrrole, polythiophene and epolyaniline. The conductive polymer may be applied as a thin film, with a preferred thickness of from about 0.1 to about 100 μιτι, on any suitable substrate, such as Pt or stainless steel. The polymer film may be prepared by chemical synthesis or preferably by electro-synthesis. A specific example is a cathode obtained by electrosynthesis of a stainless steel polypyrrole film. Other examples of cathode materials include metals similar to iron, steel, lead, nickel, titanium or platinum, or conductive metal oxides such as PbC> 2, N1O2, Ti4O7, N1CO2 or RuO2. Still other examples include electrocatalytic cathodes of a titanium-like material or titanium alloy coated entirely or partially with palladium or grafted with para-anthraquinone catalysts.

The cathode and anode may be produced in various geometrical shapes and may, for example, take the form of a flat plate or plate, a curved surface, a twisted surface, a punctured plate, a fisted mesh, an expanded mesh plate, a rod , or a tube. However, the anode and cathode preferably have a planar shape, more preferably in the form of a plate, mesh or plate.

Any conventional cell design can be used, preferably as short as possible between the anode and cathode. A split cell may, for example, be of the "zero backlash" type, where at least one of the electrodes is pressed against a membrane that divides the cell.

A typical production plant includes a multitude of cells to achieve the desired production rate. The cells may be arranged in a single-pole or bipolar mode on an electrolyzer according to any conventional design.

Some embodiments of the invention will now be further described in conjunction with the accompanying schematic drawings. However, the scope of the invention is not limited to these claims. Figure 1 shows a schematic configuration of the cathodic process part, while Figures 2, 3 and 4 show schematic drawings of various electrochemical cells.

Referring to Figure 1, a taming electrochemical reduction occurs in a predominantly continuous continuous phase of an electrolyte in a cell compartment 1, which may be a cathode compartment or a single-compartment cell. A feed stream 14 provides cell compartment 1 with any substances that are consumed in the process, such as oxygen, or withdrawn into any non-recycled product stream, such as water, or a similar inert nitrogen gas. If oxygen is present, a reaction between the reduced form or forms of the mediator and oxygen to hydrogen peroxide or alkali metal peroxide may also occur in cell compartment 1. If this reaction proceeds to a sufficiently large extent, it is sufficient to remove hydrogen peroxide along with for example, water in a stream 6. If the reaction to hydrogen peroxide or alkali metal peroxide is incomplete, the electrolyte is withdrawn, and the reaction completed to the desired extent in an oxidation reactor 2 where additional oxygen 15 may be supplied. A resulting stream 7 contains hydrogen peroxide, or alkali metal peroxide in one or more forms, depending on the conditions used, for example, as a vapor, or dissolved in a liquid phase. If both a gas phase and at least one liquid phase are present, they are brought into a liquid gas separator 3 from which a current from 8 is brought into a capacitor 4. Hydrogen peroxide product 10 is withdrawn from condenser 4 , while the remaining gas 13, for example oxygen, steam, and other optional components, is recycled to any point where oxygen may be used, such as cell compartment 1, or to the oxidation reactor 2, or exhausted via 16 A liquid stream 9 from separator 3 is recycled to cell compartment 1. If liquid stream 9 contains hydrogen peroxide, it is first brought to a separator 5, which, for example, may be an extraction unit, or a membrane separation unit. Here stream 5 is separated into a product stream 11 containing hydrogen peroxide and a recycle stream 12 that makes up the at least partially organic electrolyte.

The various units illustrated in Figure 1 can be combined in a multitude of ways. For example, oxygen may be introduced into cell compartment 1 in a number of ways, for example separately, or together with any recycled liquid or stream feed. Oxygen may also be introduced at a position above the electrodes in order to separate electrochemical reactions and oxidation. Oxidation reactor 2 and liquid gas separator 3 may be combined, for example, by the use of a bubble column. If the operating conditions are adjusted so that no gas forms, and only one liquid phase is withdrawn from cell compartment 1, the liquid gas separator 3 and condenser 4 may be omitted.

Referring to Figure 2, an electrochemical cell operated in accordance with the invention comprises anode 21 in an anode compartment 23, and a cathode 22 in a cathode compartment 24. The cell may also comprise a separate intermediate compartment 25 from the compartments. anode and cathode elements 23, 24 ion selective membranes 26, 27. In one embodiment, membrane 26 is anion permeable, and membrane 27 is cation permeable. In another embodiment, both membranes 26, 27 are cation permeable. The cathode compartment 24 holds a catholyte comprising an organic mediator according to the invention. Oxygen-containing gas is fed through the inlet stream 28 to the cathode chamber 24, and a discharge stream 29 comprising hydrogen peroxide and / or reduced mediator is brought to a unit 30 where further processing takes place. Such further processing may include reduced oxidation of the mediator to obtain hydrogen peroxide and its separation, resulting in a product stream comprising hydrogen peroxide and, optionally, other species, such as water, which may remain in the final product, and others which may be further separated. later, and a recycled stream 32 comprising, for example, catholyte with an organic mediator obtained by oxidizing the reduced shapes thereof. The anode compartment 23 is fed with a feed stream 33 which may have various compositions, depending on the desired reactions. The anolytes, including reaction products, are withdrawn into a discharge stream 34 in a product separator 35 from which a product 36 is withdrawn, and the remaining electrolyte 37 recycled to the anode compartment 23.

Intermediate compartment 25 is fed through an inlet stream 38 with a preferably aqueous solution, the composition of which depending on the desired total reactions. A discharge stream 39 from intermediate compartment 25 may be recycled, or otherwise used. If the cell of Figure 2 is used in one embodiment where membrane 26 is anion selective, membrane 27 is cation selective, and chloride is reacted. at the chlorine-forming anode which may be further hydrolyzed to hypochlorous acid and finally chlorate, the anolyte is preferably an aqueous solution containing NaCl, NaClO3, or the corresponding potassium salts KCl or KClO3, and optionally a buffer such as chromate, dichromate , or any other suitable salt. An anolyte product stream 34 is withdrawn and brought to the product separator 35, where alkali metal chlorate is crystallized and withdrawn 36, while the remaining electrolyte is recycled37 to the anode compartment 23. It is also possible to provide a unit (not shown) for additional reactions. to form chlorate in the withdrawal stream 34 prior to crystallization. In one option, the intermediate compartment 39 is preferably fed through the inlet stream 38 with a water-like solvent containing HCl or NaCl, and chloride ions are transferred through the anion selective membrane 26 to the anode compartment 23 where they are consumed at anode 21, to form chlorine in a first step. Then, Na + or K + are fed into the decathode compartment 23 through the inlet stream 33, for example as NaOH or KOH. In another option, the intermediate compartment 25 is fed through the inlet stream 38 with 0H ~, for example as NaOH or KOH, the hydroxide ions will be transferred through the anion selectively membrane 26, and chloride ions are then fed through the inlet stream. 33, for example, as NaCl. In any optional cations, usually Na + or H + are transferred from the intermediate compartment 25 through the selective cation membrane 27 in the cathode compartment 24.

Referring to Figure 3, an electrochemical cell operated according to the invention comprises anode 21 in an anode compartment 23, and a cathode 22 in a cathode compartment 24. However, in contrast to the cell Figure 2, there is only one ion membrane selective27, which is preferably cation selective, and there is no intermediate compartment. In all other respects, the cell is identical to the cell of Figure 2, the description of which being referred to.

If the cell of Figure 3 is provided with a cation-membrane selectable membrane 27, and is used in one embodiment where chloride reacts on anode 21 to form chlorine which is further hydrolyzed to form chlorate, the anolyte is preferably an aqueous solution comprising NaCl, NaClO3, or salts. corresponding potassium salts KCl or KClO3, and a buffer such as chromate or any other suitable salt. NaCl or KCl is fed into the anode compartment 23 via the inlet stream 33, while such as Na + or H + are transferred through membrane 27 into the cathode compartment 24. In order to compensate for the loss of Na + or K + through the membrane 27, To neutralize H + formed in anodic reactions, it may be appropriate to add some NaOH or KOH at any suitable position, for example, to inlet stream 33 or recycled stream 37. In all respects, similar to product handling 34 and recycle streams 37, operation is equivalent to the corresponding embodiment in the cell of Figure 2, the description of which is referred to.

Referring to Figure 4, an electrochemical cell operated according to the invention comprises anode 21 in an anode compartment 23, and a cathode 22 in a cathode compartment 24. However, in contrast to the cell 2, the intermediate compartment is replaced by a bipolar membrane 40 separating cell compartments 23, 24. Bipolar membrane 40 comprises an anion selective membrane 26 and a decation selective membrane 27 laminated on either side of a decatalyst layer 45. Water from the anolyte passes into the decatalyst layer where it it is divided into protons that pass through the cathode compartment 24, and hydroxide ions that pass through the anode compartment 23. In all other respects, the cell is identical to those of Figures 2 and 3, the descriptions being referred to.

If the cell of Figure 4 is used in an embodiment where chloride reacts on anode 21 to form chlorine which is further reacted to form chlorate, the anolyte is preferably an aqueous solution comprising NaCl, NaC103, or the corresponding potassium salts KCl or KCIO3, and a buffer. , such as chromate, or any other suitable salt. NaCl or KCl is fed into the anode compartment 23 through the inlet stream 33. Inside the bipolar membrane, the water is divided into protons and hydroxides. Protons move in the cathode compartment34, and facilitate oxidation of reduced mediator to form hydrogen peroxide, while hydroxide ions move in the anode compartment 23, facilitating chlorine hydrolysis. In other respects, similar to product handling 34 and recycle streams 37, the operation is equivalent to the corresponding embodiments performed in the cell of Figure 2, the description of which being referred to.

In all embodiments described in Figures 2-4, the cathodic process may be the same, that is, domestic reduction in cathode 22, and transfer of H + or Na + cations from intermediate compartment 25, or from anode compartment 23 through the selective decation membrane 27.

The invention will now be described by the following examples. If not otherwise stated, all parts and percentages refer to parts and percentages by weight.

Example 1:

A solution containing 50 ml of the 1-butyl-3-methyl-imidazolium hexafluorphosphate [BMIM] [HFP] ionic liquid with 0.8 g of 2-ethyl-9,10-anthraquinone (EAQ) was poured into the cathode compartment of a small reactor. . Water-saturated gas was purged in the solution for 30 minutes to dissolve gases in the solution, and to saturate the solution with water to an estimated content of about 3-5 weight%.

At the top of the organic phase, a 40 ml aqueous phase of 40.5 M H2SO4 was added to supply protons. A circular platinum mesh cathode with a diameter of 3 cm was placed in the organic phase, and a platinum mesh anode was placed in a separate compartment containing 10 mM aqueous NaOH solution. The anode and cathode compartments were separated with a non-selective ceramic membrane (diaphragm). The catholyte was stirred by a magnetic bar located in the organic phase in the cathode compartment.

To keep track of cathodic potential, a Calomel reference electrode was placed in the cathode compartment next to the cathode. The cathode compartment contained an aqueous solution of 150 g / l NaCl and 10 g / l desodium dichromate. At a temperature of 68 ° C, a current of 0.2A was placed between the anode and cathode. During the experiment, a few drops of NaOH (IM) were added to the anolyte to maintain the pH between 6 and 7. In the cathode compartment, hydrogen peroxide was generated. In the anode compartment, chloride was oxidized to chlorine, which eventually formed chlorate. After 20 minutes, the experiment was completed, and a current efficiency for declorate formation was calculated at 59%.

Claims (19)

1. A process for the production of alkali metal chlorate, characterized in that it comprises: providing an electrochemical cell comprising anode and cathode in anode and cathode-separated compartments, cathode contact with an electrolyte comprising at least one organic mediator and one or more. more organic or mineral acids; reaction of the organic mediator in the cathode to form at least one reduced form of the mediator; reaction of at least one reduced form of the mediator with oxygen to form hydrogen peroxide; contact of the anode with an alkali metal chloride; chloride at the anode to form chlorine which is hydrolyzed; hydrolyzed chlorine to form chlorate. 2. A process according to claim 1 wherein the concentration of ionschlorides in the anolyte is from about 30 to about 300 g / l calculated as sodium chloride. Process according to any one of claims 1-2, characterized in that the pH in the anolyte mass is from about 4 to about 10. 4. A process according to any one of claims 1-3, characterized in that the electrochemical cell comprises at least one compartment between the anode and cathode compartments. A process according to any one of claims 1-4, characterized in that the organic mediator is selected from the group consisting of quinones, flavoquinones, depyridine derivatives, and ketones. 6. A process according to claim 5 wherein the organic mediator is selected from the group consisting of quinones containing a (benzo) quinone moiety. 7. A process according to claim 6 wherein the organic mediator is selected from the group consisting of anthraquinones, tetrahydro anthraquinones, naphthoquinones, and their derived benzoquinones. 8. A process according to any one of claims 1-7, characterized in that the organic mediator content, including the reduced forms, nocatolyte is at least 1 weight%. 9. A process according to any one of claims 1-8, characterized in that the catolite comprises at least partially organic salt, comprising at least one type of organic cation and / or organic anion. 10. A process according to claim 9 wherein the at least partially organic salt content in the catholyte is about 20 weight% about 99 weight%. 11. A process according to any one of claims 9-10 characterized in that the less partially organic salt is present together with a neutral co-solvent, and the weight ratio of salt to co-solvent is about 1. : 1 to about 1000: 1. 12. A process according to any one of claims 9-11, characterized in that the neutral cosolvent is present in the catholyte in an amount of up to about 50 weight%. 13. A process according to any one of claims 9-12, characterized in that the less partially organic salt than itself or in combination with a neutral co-solvent forms a liquid phase at atmospheric pressure below 130 ° C. 14. A process according to any one of claims 9-13, characterized in that the less partially organic salt at 100 ° C has a partial pressure below about 10 kPa. 15. A process according to any one of claims 9-14, wherein the least partially organic salt comprises a cation selected from the group consisting of 1-alkyl-3-methyl imidazolium, 1-butyl-3-methyl. imidazolium [BMIM], 1-ethyl-3-methyl imidazolium [EMIM], 1,2,3-trimethylimidazolium, N-alkylpyridinium, N-butyl pyridinium [BPY], pyrrolidinium, guanidinium and alkyl guanidinium, isouronium, PR4 +, NR4 +, SR3 +, tetramethylammonium, choline, cocomonium, and mixtures thereof, R independently of each other being optionally alkyl, alkenyl or substituted aryl, or hydrogen. 16. A process according to any one of claims 9-15, characterized in that the less partially organic salt comprises a cation selected from the group of substituted quinones. 17. A process according to any one of claims 9-16, characterized in that the least partially organic salt comprises an anion selected from the group consisting of hexafluorphosphate [HFP], tetrafluorborate [TBF], fluororsulfonate, hexafluorantimonate hexafluorarsenate, chloraluminate, bromoaluminate, bis (trifluoromethylsulfonyl) imide, tris (trifluoromethylsulfonyl) metide, tricianometide, dicyanamide, nanofluoromethanesulfonate, trifluoromethanesulfonate, 2,2,2'-trifluoromethanesulfonate, nitrate, sulfate, RPO42 ", R2PO4-, e.g. ), perchlorate, acetate, alkylsulfonate, bis (2-ethylhexyl) sodiumsulfosuccinate, diethylene glycolmonomethylethersulfate, alkyloligoetersulfate, pivalate, tetraalkylborate, propionate, succinate, saccharate, glycolate, stearate, lactate, malate, tartrate, benzoate, citrate methanesulfonate, toluenesulfonate, mixtures thereof, R independently of each other, optionally alkyl, yl, alkenyl or substituted aryl, or hydrogen. 18. A process according to any one of claims 9-17, characterized in that the least partially organic salpel comprises an anion selected from the group consisting of substituted quinones. 19. A process according to any one of claims 9-18, wherein the least partially organic salt comprises a cation selected from the group consisting of [1,3-dialkylimidazolium], [trialkyl ammonium], [tetraalkyl ammonium]. ], [trialkylphosphonium], [tetraalkylphosphonium], [alkylpyridinium], [choline], [Q-NR3 "1"] and [Q-PR3 "1"], and an anion selected from the group consisting of [sulfate], [ phosphate], [alkyl sulfate], [alkyl sulfonate], [dialkyl phosphate], [alkyl phosphonate], [Q- (O) -SO3] and [Q- (O) -PO3R], where Q is a quinone, ( O) is an optional oxygen, and R is independently of each other, optionally alkyl, alkenyl or substituted aryl, or hydrogen.